1. Field of the Invention
The present invention relates to a stay housable type motor driven mirror to be installed on vehicles and the like.
2. Description of the Prior art
According to well-known stay housable type motor driven mirrors of this kind, a foundation of a stay supporting a mirror of the vehicle is rotatably held in a bracket case to be attached to a body of the vehicle, and the stay is rotatably driven by a motor installed in the bracket case so as to controllably move the mirror.
According to such a conventional stay housable type motor driven mirror, a of relatively long is stay provided with a mirror glass and a mirror body, respectively attached to its top end and the stay is held or supported by a bracket case relatively small in size, so that when the bracket case attached to a vehicle body shakes a little, the top end of the stay connected to the bracket case largely shakes, because a small degree of shake of the bracket case attached to the vibrating vehicle body is magnified many times at the top end of the long stay, resulting in considerable shaking of the mirror device. In particular, ordinarily a radial-directed load is effected to the foundation of the stay when the drive motor transfer its power to the mirror device, and additionally windage or wind-breaking resistance attacks the mirror body at the top end of the stay, thereby play is apt to be generated between the bracket case and the stay. In addition, the conventional stay housable type motor driven mirror is adapted to directly drive or rotate the stay by the drive motor, resulting disadvantageously in a large drive mechanism such as a motor.
Accordingly, the applicant of the present invention developed, in order to solve the shortcomings of the conventional stay housable type motor driven mirror, a novel stay housable type motor driven mirror and filed it with the Japan Patent Office as Utility Model application No. 61-98885 (UM laid-open No. 3-22041). According to the applicant's device, a stay of the stay housable type motor driven mirror can be supported in a stable condition without any generation of play and additionally a drive mechanism of the mirror can be minituarized.
Of the drawings of the present invention, FIG. 7 is a side elevation of one example of such a conventional stay housable type motor driven mirror, FIG. 8 is a transversal section showing an interior construction of the mirror, FIG. 9 is an exploded perspective view of the construction, FIG. 10(a) depicts a section of an operative relation between a support shaft and a follower gear before the gear rotates and FIG. 10(b) shows another section similarly to FIG. 10(a) after the gear rotates.
According to the stay housable type motor driven mirror, a mirror body 2 supporting a mirror glass is attached to a top end of the stay 1 curved about in a shape of crank, a foundation of the stay 1 is assembled into a bracket case 4 attached to a vehicle body 3. The stay 1 is driven by a drive mechanism 5 installed in the bracket case 4. The drive mechanism 5 is adapted to transfer power of the drive motor 6 to the support shaft 11 supporting the stay 1 through speed reduction mechanism 7, clutch mechanism 8, drive gear 9, and follower gear 10 so as to rotate the shaft 11. As shown in FIG. 8, the support shaft 11 has a reducing lower end 12aand an enlarged upper end or flanged portion 12. The lower end 12ais engaged with the follower gear 10 with a play along a predetermined direction. Rotational force of the follower gear 10 can be transferred to the support shaft 11 after the rotation passes such play zone.
There is a first engagement means 15 between facing faces of the upper flanged portion 12 and an upper lid 14 of the bracket case 13. There is a second engagement means 17 between the follower gear 10 and a lower lid 16 of the bracket case 13. The first engagement means 15 consists of a groove 18 formed on a rear side of the flanged portion 12 of the support shaft 11 and a convex portion 19 formed on the upper lid 14 of the bracket case 13. This groove 18 and the convex portion 19 are engaged with each other. The second engagement means 17 consists of a slanted concave portion 20 of the follower gear 10, an hole 22 formed on the lower lid 16 of the bracket case 13, and a ball 21 placed in the concave portion 20 and the hole 22.
The sectional shape of the slanted concave portion 20 is similar to a saucer and the ball 21 can ride or climb along the slanted side wall of the saucer.
When the drive motor 6 of the drive mechanism 5 drives the drive gear 9 and rotation of the drive gear 9 is transferred to the follower gear 10, first the support shaft 11 moves upward until the follower gear 10 contacts the reducing lower end portion 12aof the support shaft 11 go as to release an engagement condition of the ball 21 of the second engagement means 17 and the concave portion 20 of the follower gear 10, simultaneously release another engagement condition of the convex portion 19 of the first engagement means 15 and the groove 18.
It is noted that the first engagement means 15 is a combination of the groove 18 and the convex portion 19, and
second engagement means 17 is a combination of the slanted concave portion 20, the ball 21 and hole 22. An urging and resilient force of a coil spring 23 makes them combined in order to prevent the support shaft 11, or the stay 1 from rotating.
Consequently, when driving of the drive mechanism 5 rotates the follower gear 10, the ball 21 climbs the slanted side wall of the slanted convex portion 20 and an engagement condition of the second engagement means 17 is released against the resilient force of the spring 23. Simultaneously, the support shaft 11 is pushed up and the engagement condition of the first engagement means 15 is released or disengaged, the follower gear 10 rotates the support shaft 11 after rotation of the gear 10 passes the play zone, and the stay 1 rotates, thus moving the mirror body 2.
The clutch mechanism 8 placed at a drive side of the stay housable type motor driven mirror according to the present invention has a pair of convex portion 26 and concave portion 25, respectively formed on an upper face of the drive gear 9 and a lower face of the pressing plate 24. During a driving period of the motor driven mirror, the convex portion 26 and concave portion 25 are engaged with each other, so a force of the drive motor 6 and the speed reduction gear mechanism 7 is transferred from the pressing plate 24 to the drive gear 9, rotating the follower gear 10 as described above. When the mirror body 2 is given some force from the outside, the stay 1 has a large load or stress, and rotation force is transferred reversely from the follower gear 10 to the drive gear 9, an engagement of the clutch mechanism 8 is disengaged resisting a force of the spring 27, no load is applied to the speed reduction gear mechanism 7, and the drive motor 6 is prevented from injuring itself such as burning and the like.
As described above, in the stay housable type driven mirror of the present invention, the engagement means 15 and 17 adapted to be effective by spring force supports the support shaft 11 without play or firmly resulting a stable holding of the stay 1 of the motor driven mirror. In addition, because the support shaft 11 for holding and rotating the stay 1 doesn't rotate before these first and second engagement means 15 and 17 are disengaged, it is possible to drive or rotate the stay 1 or support shaft 11 by a drive mechanism of relatively small in size.
However, when the mirror body 2 of the conventional stay housable type motor driven mirror takes an outside force and the support shaft 11 is compulsorily made to rotate, a load of the outside force is transferred to the drive gear (small gear) 9 since the clutch mechanism 8 having a shock absorbing function is installed on the drive gear 9. Consequently, a design allowance of a clutch holding torque is made small and it fears that suitable shock absorbing effect is not attained. In addition, because a clutch engaging spring 27 is installed at the driving side of the motor driven mirror, the height of the drive mechanism including the clutch mechanism disadvantageously increases resulting in a large size of whole construction of the mirror.
Additionally, according to the prior art of the mirror, the drive motor 6, speed reduction gear mechanism 7, and drive gear 9 are longitudinarily arranged, thereby a height H of the bracket case 14 increases, a degree of freedom in designing of the motor driven mirror, when it is attached to the vehicle, decreases, and design allowance of size of construction parts and arrangement of them in an interior of the bracket case 14 is not sufficient.